The intensely felt need to see and experience the world by travelling to and/or living in other countries. Mostly caught during the first early travel experiences and very hard to dispose of. Could also be defined as synonym for wanderlust or itchy feet.
The strange and gnawing feeling when you return from travelling and finally arrive at home that tells you that somehow you're in the wrong place and should just get your stuff cleaned and packed again instead, and get on the next available cab to the airport. That's when the gypsy bug bites you.